Question: Simplify the following expression: $t = \dfrac{7}{5r} - \dfrac{1}{6r}$
Solution: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $5r$ and $6r$ $\lcm(5r, 6r) = 30r$ $ t = \dfrac{6}{6} \cdot \dfrac{7}{5r} - \dfrac{5}{5} \cdot \dfrac{1}{6r} $ $t = \dfrac{42}{30r} - \dfrac{5}{30r}$ $t = \dfrac{42 -5}{30r}$ $t = \dfrac{37}{30r}$